Communication systems are known to employ power control methods that control forward-link transmission energy. Once such communication system employing forward-link power control is a spread-spectrum communication system. Because many forward-link signals in a spread-spectrum system are typically transmitted on the same frequency, a majority of the noise (which is inversely proportional to bit energy per noise+interference density i.e., E.sub.b /N.sub.0) associated with a received signal can be attributed to other forward-link transmissions. The magnitude of this noise is directly related to the received signal power of each of the other forward-link transmissions. Thus it is beneficial for cellular infrastructure equipment (such as a cellular base station) to transmit with a forward-link gain at the lowest level possible that insures acceptable transmission quality.
The current method of controlling forward-link power in a code-division, multiple-access (CDMA) communication system is described in Cellular System Remote unit-Base Station Compatibility Standard of the Electronic Industry A36,283dustry Association Interim Standard 95 (TIA/EIA/IS-95-A). (EIA/TIA can be contacted at 2001 Pennsylvania Ave. NW Washington D.C. 20006). During TIA/EIA/IS-95-A call origination, initial forward-link gain must be set high enough to guarantee an acceptable link. Since the channel between the base station and the remote unit is unknown at the time of origination, the call is originated at a maximum forward-link gain and then powered down accordingly. Because TIA/EIA/IS-95-A forward-link power control is very slow to update (on the order of once every four seconds), the base station can transmit at an unacceptably high forward-link gain for extended periods of time, needlessly contributing to system noise.
Thus a need exists for a method and apparatus for power control in a spread-spectrum communication system that reduces the time a base station transmits at an unacceptably high forward-link gain.